1、由连词that引导的主语从句。
例如：That you will win the medal seems unlikely.
你想获得奖牌看起来是不可能的。
That you are so indifferent bothers me.
你如此冷淡使我很烦恼。
That she survived the accident is a miracle.
她在事故中幸免于难简直是奇迹。
2、用连接代词或连接副词if, whether 引导的主语从句。
例如： Which of them escaped from the prison is still a mystery.
他们哪一个是从监狱里逃跑的，仍然是个谜。
When they will come hasn’t been made pubic.
他们什么时候来还不知道。
Whether she is coming or not doesn’t matter too much.
她来不来都无关紧要。
3、用关系代词引导的主语从句。
例如：What you need is more practice.
你所需要的是更多的训练。
What I want to know is this. 我想知道的就是这事。
Whatever we do is to serve the people.
我们无论做什么都是为人民服务。
4、主语从句可以直接放在主语位置上，也可以用it作形式主语，而将从句放在句末（尤其是当谓语较短时）。
例如：That light travels in straight lines is known to all.
扩展资料
主语从句，即在复杂句中充当主语成分的句子，例如"That he finished writing the composition in such a short time surprised us all"，他在很短的时间内写完作文让我们都很惊讶，此复合句主要描述的是某事让我们惊讶，某事就是该复合句的主语，因此“That he finished writing the composition in such a short time”便是该复合句的主语从句。
引导主语从句的连词主要有：
从属连词：that whether
连接代词：who whoever whom whose what whatever which whichever
连接副词：when where how why
小结:
（1）引导主语从句连词有that,whether,who,what,whatever等
（2）连词位于句首不能省略
（3）主语从句大多数情况下视为第三人称单数，但也有例外，如例（9）
注意：当what引导的名词性分句作主语时，主谓一致问题极为复杂。
参考资料：百度百科——主语从句
1. 主语从句位于句首的句型
1) 由that 引导的主语从句
That he hasn't phoned is odd. 他还没来电话很奇怪。
That she will win the first seems impossible. 她赢得第一好像不大可能。
2) 由连接代词或连接副词引导的主语从句
What you need is a faster computer. 你需要的是一部更快的计算机。
Which of them are more reliable requires further test. 需要进一步的测试来了解它们中哪一个更可靠。
When she'll be back depends on the weather. 她什么时候将会回来取决于天气。
Where she has gone is not known yet. 她去了哪儿，还不知道。
How the prisoner managed to escape is still unknown. 仍然不知道犯人是如何设法逃跑的。
Why they suddenly disappeared still remains a mystery. 他们为什么突然间消失仍然是一个谜。
Whoever is responsible will have to pay for the damage. 无论是谁负责都必须赔偿损失。
Whether she is coming or not doesn't matter at all. 她来不来根本无关紧要。
3) 由 just because 引导的主语从句
由just because 引导的主语从句通常只用于 "Just because...doesn't mean..."句型中。
Just because it is legal doesn't mean it is ethical. 仅仅是符合法律并不意味着一定就合乎伦理。
Just because something has value doesn't mean it has a price. 有价值的东西并不一定就有价格。
2. 以it作形式主语的主语从句
1） it + be + 形容词 + 主语从句
It is unclear when he will come. 不清楚的他什么时候会来。
It is essential that we remember all the key points before the exams. 考试前记所有要点非常关键。
2） it + be + 名词 + 主语从句
It is common knowledge that fish can't live without water. 众所周知，鱼没有水就不能存活。
It is a good thing that we have so many tools. 我们有这么多工具是一件很好的事情。
3） it + 及物动词 + 宾语 + 主语从句
It makes no difference whether we go by train or by bus. 我们坐火车去还是坐公共汽车去都没有什么区别。
It shocked me that Peter did not tell anybody where he was. 让我吃惊的是彼得没有告诉任何人他在哪里。
4） it + 动词的被动语态 + 主语从句
It is estimated that the meeting will last four days. 这次会议预计将持续4天。
It has not been announced when the plane will take off. 还没有宣布飞机什么时候起飞。
5) it + 不及物动词 + 主语从句
It happened that my mother was out that day. 我母亲恰巧那天出去了。
It turns out that she was a friend of my sister. 结果是她是我姐姐的一个朋友。
6）it + be + 介词短语 + 主语从句
It is of great importance whether we can arrive there by 7:00pm. 我们是否能在晚上七点前到达那里非常重要。
7) 注意主语从句后移时, 引导词that 有时可以省列。
It was clear his words pleased her. 显然他的话使她很高兴。
It's a pity he can't swim. 很遗憾他不会游泳。
例如：That you will win the medal seems unlikely.
你想获得奖牌看起来是不可能的。
That you are so indifferent bothers me.
你如此冷淡使我很烦恼。
That she survived the accident is a miracle.
她在事故中幸免于难简直是奇迹。
2、用连接代词或连接副词if, whether 引导的主语从句。
例如： Which of them escaped from the prison is still a mystery.
他们哪一个是从监狱里逃跑的，仍然是个谜。
When they will come hasn’t been made pubic.
他们什么时候来还不知道。
Whether she is coming or not doesn’t matter too much.
她来不来都无关紧要。
3、用关系代词引导的主语从句。
例如：What you need is more practice.
你所需要的是更多的训练。
What I want to know is this. 我想知道的就是这事。
Whatever we do is to serve the people.
我们无论做什么都是为人民服务。
4、主语从句可以直接放在主语位置上，也可以用it作形式主语，而将从句放在句末（尤其是当谓语较短时）。
例如：That light travels in straight lines is known to all.
例如：That you will win the medal seems unlikely.
你想获得奖牌看起来是不可能的。
That you are so indifferent bothers me.
你如此冷淡使我很烦恼。
That she survived the accident is a miracle.
她在事故中幸免于难简直是奇迹。
2、用连接代词或连接副词if, whether 引导的主语从句。
例如： Which of them escaped from the prison is still a mystery.
他们哪一个是从监狱里逃跑的，仍然是个谜。
When they will come hasn’t been made pubic.
他们什么时候来还不知道。
Whether she is coming or not doesn’t matter too much.
她来不来都无关紧要。
3、用关系代词引导的主语从句。
例如：What you need is more practice.
你所需要的是更多的训练。
What I want to know is this. 我想知道的就是这事。
Whatever we do is to serve the people.
我们无论做什么都是为人民服务。
4、主语从句可以直接放在主语位置上，也可以用it作形式主语，而将从句放在句末（尤其是当谓语较短时）。
例如：That light travels in straight lines is known to all.
光沿直线传播，这是众所周知的事。
=It is known to all that light travels in straight lines.
众所周知光沿直线传播。
When the plane is to take off has not been announced .
飞机何时起飞还没有宣布。
= It has not been announced when the plane is to take off.
还没有宣布飞机何时起飞。
当what引导的主语从句表示“…的东西”时，一般不用it作形式主语。
错:It is a book what he wants.
对:What he wants is a book. 他想要的是本书。
如果带主语从句的句子是疑问式，则必须用it作形式主语的结构。
例如：Has it been settled who will be sent to carry out the task ?
谁将被派去执行这项任务决定了吗 ？
